Stabilized gasoline



jan. lg, H943. R. H. ROSENWALD ET AL 2,308,782

STABIMZED vGAsomNx:

Original Filed April 50, 1958 U D/Lh/YL .SUBS [TUT SUBSTITUZD Hill@ GSOLINE Robert ll. Rosenwald an Chicago, lill., assignors ucts Company, Chicgil,

Delaware d .loseph A. Chenicek, to Universal Oil Prodllll., a corporation of original application april 3o, 193s, sen-'iai No. 205,350, now Patent No. 2,250,501, dated .luly

, 29, 1941. Divided and 1941, Serial No. 387,466

4 Claims.

This application is a division of our co-pending application Serial No. 205,356 filed April 30, 1938, now Patent No. 2,250,501, of July 29, 1941.

This invention relates more particularly to a process of treatment applicable to lower boiling fractions of cracked distillates within-the gasoline range although-it is also applicable to heavier distillates produced by the fractionation of cracked products and to corresponding fractions from the primary distillation of crude petroleums or other hydrocarbonaceous materials such as coal and shale.

The process is concerned specifically with the use of certain definite types of inhibitors to materially arrest the deterioration to which hydrocarbon distillates containing appreciable quantities of olefinic and other unsaturated hydrocarbons are subject. The art of using inhibitors in unstable gasolines is now one of comparatively long standing and a large number of individual compounds and classes of compounds have been developed for practical use, all of which apparently possess the characteristic of being more or less readily oxidizable so that the peroxidic compounds Which are primarily formed when olencontaining gasolines are in contact with air or other oxidizing gas mixtures are decomposed and the sequence of the chain reactions leading to the formation of higher boiling polymers and resinous products which cause the deterioration of the gasoline in respect to color, gum content, and antiknock value is stopped for a time depending upon the emciency of the inhibitor, the degree of unsaturation of the oil and the extent of its exposure.

, It is recognized that the inhibitor art is known to include the use of such compounds as phenols, amines, and aminophenols and crude primary products containing these compounds, and I no basic claim is made herein to the broad use of any of these classes. The present invention is specially concerned with a limited group of compounds which have been found to possess exceptionally good inhibiting potency combined with resistance to accidental removal by contact with water or caustic soda. which occurs at many points in the storage systems of oil refineries.

In one specic embodiment the present invention comprises the treatment of unstable gasolines, particularly cracked gasolines, to materially arrest ,the deterioration thereof by adding to said gasolines relatively small percentages of N-methyl-N-heptyl aminophenols. ,The heptyl groups may be of a normal or branched character 'and the substituted amino group may be in the this application April 8,

ortho, meta, or para position with respect to the hydroxyl group although in general the compounds of greater potency fall within the general class of those of the para substituted variety.

We have shown as a result of considerable number of experiments in which differently substituted alkyl aminophenols were tested that greater advantages are gained by utilizing as inhibitors alkyl amino-phenols in which there is substitution of both amino hydrogens by different alkyl groups over utilizing those characterized by substitution with identical groups or by substitution of one amino hydrogen with one group even though the total number of carbon atoms in the substituting groups is the same in all cases. The advantages gained include greater inhibiting potency, greater solubility in gasolines and improved resistance to extraction with Water or alkaline solutions to which gasolines maybe exposed during storage conditions, on account of the decreased solubility of the mixed substituted compounds. These advantages were unexpected and unpredictable from any study of chemical composition or constitution relating to inhibitors and form the principal subject matter of the present invention. The actual degree of these eliects will be indicated in aA succeeding illustrative and numerical section.

Compounds of the present character are made from amino phenols -by successively replacing the amino hydrogens with the desired alkyl groups. These step-wise substitutions are made generally by the interaction 'of molal proportions of an amino-phenol with an alkyl chloride for an alkyl sulfate using an alkaline condensing agent according tol the following equations which show the manufacture of N-methyl-N-iso-amyl paminophenol:

@wenn ,mum

I- N'- l- C5H|| Methyl chloride C Ha- N- l'- 05H N-methyl-isoamyl-p-amlno phenol In this method the reaction may be brought about in a solvent such as ethyl alcohol and it is desirable to have present an amount of a carbonate or bicarbonate molecularly equivalent to the amount of alkyl halide. A catalyst is not necessary.

The following specic example is given of the manufacture of a compound falling within the scope of the invention, the method shown being definitely applicable to the manufacture of other similar compounds by varying the alkyl groups in the reactants according to their relative molecular weights.

To prepare N-n-octyl-N-methyl-p-aminophenol, the mixture tabulated below was refiuxed for 12 hours under atmospheric pressure.

Parts by weight Methyl-p-aminophenol sulfate 45 Sodium bicarbonate 52 n-Octyl bromide 45 Ethyl alcnhnl 200 Redistillation of fraction II which corresponded to a 70% yield of the desired compound showed a constant boiling point `of 163 C.

The amounts of the present classes of compounds which are necessary to properly inhibit the deterioration of unstable gasolines will obviously depend upon the instability of the particular gasoline at hand and the potency of the individual compound selected. As a rule it is seldom necessary to employ more than 0.1% of any of the inhibiting compounds and usually percentages of the order of 043% are suiiicient. Since the present compounds are`- considerably more soluble in gasoline than those in which the alkyl groups are the same, the addition of the necessary small amounts to gasoline contained in large storage tanks is more simple and more easily effected than when inhibitors of lesser solubility are employed in which cases it is frequently necessary to employ along period of mechanical mixing or an auxiliary solvent to assist in the dispersion of the inhibiting compounds. In the present instance a minimum of mixing is required and solvents are not necessary. In addition, owing to the relatively low water and solubility of thepreferred compounds, they may be used Boiling in gasolines which are not dry or which are stored over water or alkali to prevent corrosion of the tank bottoms. These inhibitors may be also employed in commotion with other compounds of specific character such as the dyes which are frequently used to mask the slightly yellow tinge characteristic of cracked gasolines, with various types of antiknock compounds such as tetra ethyl lead and with special types of inhibitors which are directed to the preservation of color or other speciiic properties.

The attached curves. designated as Figure 1, are introduced to exemplify the more general aspects of the invention. 'I'hese curves are made up to indicate the data obtained in a large number of experiments. Referring to the iigure it will be seen that curve 1 shows the variation of the eiective inhibitor ratio with the total carbon atoms in substituting groups of mono-alkyl substituted aminophenols. Curve 2 shows the same relationship when di-alkyl substituted compounds are considered in which the substituting groups are the same. Curve 3 which it will be observed is higher than the other two at all points below 18 carbon atoms shows graphically the data obtained with mixed alkyl substituted aminophenols. In this case one of the subsequent groups was a methyl group. A representative compound of the present invention, namely N-methyl-N-heptyl-p-aminophenol, contains a total of 8 alkyl carbon atoms in the substituting groups and is shown to have an effective inhibitor ratio of approximately 1.2. From this data it is obvious that the most effective inhibitors are those di-substituted aminophenols in which the substituting groups are dierent.

We claim as our invention:

1. A process for the treatment of gasolines subject to deterioration of their desirable properties on storage, which comprises adding thereto amounts of N-methyl-N-heptyl-aminophenols equal to'less than 0.1% by weight of said gasoline.

2. A process for the treatment of gasolines subject to deterioration of their desirable properties on storage, which comprises adding thereto amounts of N-methyl-N-heptyl-p-aminophenols cliual to less than 0.1% by Weight of said gaso- 3. A process for the treatment of cracked gasolines subject to deterioration of their desirable properties on storage, which comprises adding thereto amounts of N-methyl-N-heptyl-p-aminophenol equal to less than 0.1% by weight of said gasoline.

4. Motor fuel comprising unstable gasoline containing a relatively small amount of N- methyl-N-heptyl-p-aminophenoL ROBERT H. ROSENWALD. JOSEPH A. CHENICEK. 

